jondallimore
Posts: 207
Joined: Thu Aug 04, 2016 11:02 pm

Run fan off USB port

Thu Aug 08, 2019 2:55 pm

Hello,

with a pi 4 - I want to keep the GPIO pins for something else.

Is there any reason I couldnt run a 5v fan from one of the USB ports?
I assume I could use a USB 2.0 port - ideally I dont want to 'waste' a USB 3.0 port.

Also is there any way to turn USB ports on and off?

thanks
Jon

trejan
Posts: 566
Joined: Tue Jul 02, 2019 2:28 pm

Re: Run fan off USB port

Thu Aug 08, 2019 3:03 pm

jondallimore wrote:
Thu Aug 08, 2019 2:55 pm
Is there any reason I couldnt run a 5v fan from one of the USB ports?
You only have 1.2A in total across all 4 USB ports. If your fan and any other USB peripherals doesn't exceed that then you should be okay. Test it first.
jondallimore wrote:
Thu Aug 08, 2019 2:55 pm
I assume I could use a USB 2.0 port - ideally I dont want to 'waste' a USB 3.0 port.
Yes.
jondallimore wrote:
Thu Aug 08, 2019 2:55 pm
Also is there any way to turn USB ports on and off?
Yes but you turn on/off all 4 ports together. You can't control power to individual ports. Use https://github.com/mvp/uhubctl

jondallimore
Posts: 207
Joined: Thu Aug 04, 2016 11:02 pm

Re: Run fan off USB port

Thu Aug 08, 2019 3:18 pm

hmmm... current isn't a problem as one of the USB 3.0 ports is getting a powered hub, but would want to turn them off individually which wont happen... maybe I'll have to use GPIO and bugger about with it a bit to make the other stuff fit.

The other option is the Power Over Ethernet pins, but I dont know enough about that... can they be made to output 5v? and if so, how?

trejan
Posts: 566
Joined: Tue Jul 02, 2019 2:28 pm

Re: Run fan off USB port

Thu Aug 08, 2019 3:20 pm

jondallimore wrote:
Thu Aug 08, 2019 3:18 pm
hmmm... current isn't a problem as one of the USB 3.0 ports is getting a powered hub, but would want to turn them off individually which wont happen...
You can try uhubctl on your USB hub as well. Some of them do let you control power to each individual port.
jondallimore wrote:
Thu Aug 08, 2019 3:18 pm
The other option is the Power Over Ethernet pins, but I dont know enough about that... can they be made to output 5v? and if so, how?
No. Those pins connect to the center taps of the Ethernet transformers inside the socket.

jondallimore
Posts: 207
Joined: Thu Aug 04, 2016 11:02 pm

Re: Run fan off USB port

Thu Aug 08, 2019 3:27 pm

ahh you mean control the ports on the hub? thats interesting, will have a fiddle with that.



thanks

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Imperf3kt
Posts: 2766
Joined: Tue Jun 20, 2017 12:16 am
Location: Australia

Re: Run fan off USB port

Thu Aug 08, 2019 10:32 pm

The black plastic strip won the base of the GPIO can be removed with a small flat screwdriver and working gently from end to end.
Removing it will give you an additional ~2mm of pin you can solder additional wires to without interfering with hats.
55:55:44:44:4C
52:4C:52:42:41

wh7qq
Posts: 1325
Joined: Thu Oct 09, 2014 2:50 am

Re: Run fan off USB port

Fri Aug 09, 2019 9:00 pm

Imperf3kt wrote:
Thu Aug 08, 2019 10:32 pm
The black plastic strip won the base of the GPIO can be removed with a small flat screwdriver and working gently from end to end.
Removing it will give you an additional ~2mm of pin you can solder additional wires to without interfering with hats.
Good info...never thought of that.

drgeoff
Posts: 9803
Joined: Wed Jan 25, 2012 6:39 pm

Re: Run fan off USB port

Fri Aug 09, 2019 9:05 pm

Or solder to the GPIO pins on the underside of the board. The electrons cannot tell the difference.

MalPi
Posts: 9
Joined: Thu Aug 01, 2019 1:16 pm
Location: England

Re: Run fan off USB port

Sat Aug 10, 2019 12:12 pm

drgeoff wrote:
Fri Aug 09, 2019 9:05 pm
the underside of the board. The electrons cannot tell the difference.
That is true, it is because they are leptons and have no quarks.
Only the hadrons (proton, neutron etc.) have up, down, top and bottom quarks.

:o :D :mrgreen:

I'll get my coat >>>>>>

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Burngate
Posts: 6002
Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK Tralfamadore
Contact: Website

Re: Run fan off USB port

Sat Aug 10, 2019 5:16 pm

MalPi wrote:
Sat Aug 10, 2019 12:12 pm
drgeoff wrote:
Fri Aug 09, 2019 9:05 pm
the underside of the board. The electrons cannot tell the difference.
That is true, it is because they are leptons and have no quarks.
Only the hadrons (proton, neutron etc.) have up, down, top and bottom quarks.

:o :D :mrgreen:

I'll get my coat >>>>>>
I find that strangely charming

Though neutrinos, also leptons, do know left from right.

W. H. Heydt
Posts: 10882
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Run fan off USB port

Sat Aug 10, 2019 5:22 pm

Annnddd back on topic...

Here https://www.frys.com/product/5442979?si ... IN_RSLT_PG is a fan designed to run from a USB port. It even has a speed adjustment.

jondallimore
Posts: 207
Joined: Thu Aug 04, 2016 11:02 pm

Re: Run fan off USB port

Sat Aug 10, 2019 5:29 pm

ended up using a breakout board with a ribbon cable, and forcing it to accommodate some solid core wire alongside the 5v and ground pins - gives me 5v for the fan, and will build a board to switch it when 70 degrees is reached.
Prefer it to soldering as I can take it apart easier if needs be.

I think the leprechauns know the way...

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